If you know how Embraer or Bombardier have developed, and you know a bit about Tupolev, you can understand the Chinese logic and Path with C919 and even the Japanese MRJ philosophy.
Let us start with Bombardier, Embraer, and Sukhoi.
These companies are backed by medium size economies, economies in the range of USD 1.5-3.5 trillion dollars.
Russia, Canada and Brazil have relatively small domestic markets, thus Brazil and Canada needed exports to create their domestic aircraft industries, same is Russia.
MRJ is backed by a large company that makes not only aircraft but many other products, and has a relatively big domestic market.
Embraer aircraft are mainly bought in the US and Europe, thus they have good connections with the western countries in the financial and industrial areas and Brazil is not their main market.
Tupolev and Sukhoi have bad relations with the west, a relatively small domestic Market, so Tu-330 failed and Sukhoi decided to go for cheaper planes to reduce risks, so SSJ fills the same gap E-170, but it will be bought mostly in Russia with a few aircraft in the West.
C919 is backed by a very large economy, in PPP GDP as large as Europe the US, thus the Market is big, C919 is supposedly to be a Chinese counterpart of B-737 and A-320.
China is betting domestic orders will justify the program, however most of its customers are Chinese owned airliners that are backed directly by the Chinese government.
Here you can see a difference in Philosophy between Comac and Embraer, Embraer jets needed USA and European orders once they got them their jets became sold around the world.
Comac is betting Chinese orders will follow international orders, the Chinese orders are backed by the Chinese Government banks, same is the Sukhoi Project, but Sukhoi needs export orders more than C919 or ARj-21.
I can not say if it will succeed or not as a program, only that i am sure China will be a large player for sure either with a Partnership or by it self but about the program it self is not an export oriented program in the same way Embraer programs are, they might win international orders but now they have not really make an impact beyond China.